I propose to study the sequential neuronal maturation (cortical ontogenesis), the neuronal architecture and the fibrillar-neuronal organization of the cerebral cortex of normal and abnormal fetuses, prematures, newborns and young infants. These studies will be carried out primarily with the rapid Golgi method, and, in addition with other routine neuropathological methods. Three main objectives are pursued in this investigation: 1) to establish control patterns and time tables of normal events in the sequential maturation and progressive structural organization of the human cerebral cortex in the course of prenatal and early postnatal development; 2) to utilize these observations as control data in the study of the abnormal structural organization of the cerebral cortex; 3) to study the cerebral cortex of a) infants with chromosomal aberrations (13-15, 18 and 21 trisomies) known to be associated with mental retardation; b) of infants with severe respiratory distress syndrome (RDS) or prolonged use of the respirator; and c) of infants with congenital malformations involving the cerebral cortex. In addition, I propose to study the development (ontogenesis and phylogenesis) and the structural organization of the mammalian cerebral cortex in experimental animals (the cat and the hamster) and in comparative studies with man.